Supercapacitor is a novel energy storage device, and becomes one of hot spots in novel chemical power researches by virtue of high power, high energy conversion efficiency and high cycle performance. The supercapacitor is a novel environment-friendly and irreplaceable energy storage and energy saving device between conventional capacitor and rechargeable battery; and compared with the conventional capacitor, the supercapacitor has the characteristics of high charging and discharging speed, long cycle life, no pollution, wider working temperature range, frequent usage and the like, and also has an energy storage mechanism of an electrochemical battery. Precisely because of the characteristics, more and more attention is paid to the application of the supercapacitor to the fields of electric vehicles, communication, consumer and entertainment electronics, signal monitoring and the like, such as communication equipment like audio-video equipment, a Personal Digital Assistant (PDA), a telephone set, a fax machine and a computer and a household electric appliance. It should particularly be noted that a vehicle supercapacitor can meet a requirement of high power to protect a main storage battery system during the acceleration, starting and climbing of a vehicle, which improves the development of the supercapacitor to a new level. The supercapacitor appears to conform to a requirement of era development, involves multiple subjects such as materials, energy, chemistry and electronic components, becomes one of hot spots of interdisciplinary researches, and is expected to become novel green power in this century.
At present, electrode materials for the supercapacitor mainly include activated carbon materials, conductive polymers and composite materials thereof, and transition metal oxides and composite electrode materials thereof. An activated-carbon-based supercapacitor has a longer research history, is currently higher in commercialization degree and the most technologically mature, but is complex in production process, long in production cycle and low in specific capacity; it is reported that a conductive polymer supercapacitor can show high energy density, but its cycle life is much lower than that of a carbon/carbon supercapacitor and a metal oxide supercapacitor; and although extremely high energy density and power density can be achieved by metal oxides, hydrous metal oxides (such as ruthenium oxide) and carbon nanotubes, the cost of supercapacitors manufactured from these materials is much higher than that of supercapacitors manufactured from other materials. Therefore, it is necessary to develop a low-cost electrode material with greatly improved performance for button supercapacitor and wound supercapacitor.
In addition, the energy storage of the supercapacitor is implemented by adopting a porous electrode with a large specific surface area and storing energy between its double diffusion layers. Capacitance generated during charging includes: double-layer capacitance generated by the directional arrangement of electrons and ions or dipoles on an electrode/electrolyte solution interface; or electrode charging potential-related pseudocapacitance generated by the underpotential deposition and highly-reversible chemical adsorption, desorption or oxidation-reduction reaction of an electroactive substance in a two-dimensional or quasi-two-dimensional space in a surface or bulk phase of the electrode. The performance of the supercapacitor is related to the electrode material, electrolyte and employed separator, and the electrode material is the most important factor because the performance of the electrode material directly affects the performance of the supercapacitor. Currently electrode material mainly include carbon material, metal oxide and polymer material. The carbon material with higher electrical conductivity and large specific surface area is used for double-layer capacitor; and the metal oxide and polymer with higher Faradic current generated by oxidation-reduction reaction in charging and discharging processes are used for pseudocapacitor. With the limitation of the electrode material and electrolyte, currently used supercapacitors have higher requirements on the packaging of devices, and the devices are larger in size. In order to meet the requirements of miniaturization, integration and modularization of the devices at present, solid-state flexible supercapacitor appears. The solid-state flexible supercapacitor adopts a solid-state electrolyte and electrode material which is generally a flexible thin film, so that the requirements on packaging are not high, the size is remarkably reduced, and the requirements of thinness, small size and light weight of the market on the devices are met.